The huge one-tonne device demanded round-the-clock attention from the EOD Regiment - the army’s specialist bomb disposal unit - who were forced to spend more than 28-hours trying to make the bomb safe.

An MOD spokesman confirmed last night, and again this morning, that a controlled explosion was carried out on the device at 10pm on Tuesday to make it safe.

A second explosion was heard for miles across the city, shortly before 11pm - and the MOD press office suggested today that this was another controlled explosion to detonate the device.

Red spots are where bombs landed on the old Rolls Royce factory during WW2 (Image: Rolls Royce Heritage Trust)

It is the biggest Second World War bomb discovered in the city in years, underlining why original plans to move the bomb to a safer location for a controlled detonation were abandoned.

The army had originally considered moving the bomb to a nearby quarry where they could perform a controlled explosion.

Instead, lorries were used to move tonnes of sand to cover the bomb site between Paradise Street and Puma Way, and army engineers were drafted in to assist the explosives experts with making the area safe.